60Si2MnA铁轨铺设用弹条疲劳试验断裂分析

Fracture Analysis of 60Si2MnA Spring Rods for Laying Rail during Fatigue Life Test

某60Si2MnA铁轨铺设用弹条疲劳试验寿命未达到规定值,通过对断裂弹条进行断口宏观和微观形貌观察、显微组织检查、硬度测试和化学成分分析,找出了弹条的断裂性质和早期断裂原因。结果表明:该弹条为弯曲-扭转疲劳断裂;弹条早期断裂的主要原因是其原材料碳含量偏低,导致热处理后材料硬度偏低,降低了弹条的疲劳性能;弹条表层脱碳形成了网状铁素体,导致弹条易在该处形成疲劳裂纹源,是弹条疲劳寿命未达到规定值的另一个主要原因。

Fatigue life of a batch of 60Si2MnA steel spring rods didn＇t reach the required value. The failure spring rods were analyzed by means of macro and micro observation of fracture surface, metallographic examination, hardness testing and chemical compositions analysis. The results show that the failure mode of the spring rods was fatigue fracture resulting from the co-effect of bending and twisting. The main reason for the early fracture of the spring rods was carbon content of their raw material was lower than the standard required value to 60Si2MnA steel, which resulted in the hardness of the spring rods was lower than the technical requirement after heat treatment and reduced the fatigue properties of the spring rods heavily. Another reason for the shorter fatigue life was that there was net-shape ferrite structure at the local surface of the spring rods because of decarburization, which made fatigue cracking source generate easily.